Telephone-exchange system.



N0. 760,573. E ,PATENTED MAY- 24, 1904. I

' c. E. SGRIBNER.

' TELEPHONE EXCHANGE SYSTEM.

.APrLwA'rIo ILED sEPT. 15. 1902.

N0 MODEL.

I wfrNEsSEs y 5 ATTORNEY UNITE-n iatented May 24,1904.

PATENT OFFICE- OHARL sE. sonrBnER', OF JERIOHO; VERMONT, ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF CHICAGO, LLinors, CORPORATION OF I,

ILLINOIS.

'- TELEPHONE-EXCHANGE'ISVYSTEM,

- SPECIFICATION? forming partlofiLettersiPatent no. 760,573,1dated May 24, 1904. Application filed September 15, 1902; Serial No. 123,402,: (No model.)

- 1'0 aZZ whom it may concern;- Beit known that I, CHARLES E; SCRIBNER, a -citizenof theUnited States, residing at J ericho', in. the county of Chittenden and State of Vermont,'have invented a certain new and use- 1 ful Improvement in Telephone-Exchange Systerns, of which the following is a full,: .clear,

concise, and exact description. I Y

My invention relates to a telephoneexchange system, and more particularly to a'system o fvthe type whereincurrent 'for'the tele-l phonic transmission and signaling apparatus is supplied from a centralized source of ourdition thereto in connectionwith the local sig naling-circuits The use of three conductors in the circuitinvolves the necessity of employing plugs, ijacks, and associated apparatus '1 having a like number of parts.

' Where conditions are such as not to require the termination of a great number of telephoneelin'es in I alimited space, the employment of such systemsis permissible; but where considerations of economyand efficient operation require that a great many'linesrbe provided with terminals within the reach of a single operator it is desirable to reducethe'conductors in'the I switchboard for each line to the smallest num: ber possible consistent with theproper operation of the automaticsupervisorysignalsand efiicient transmission of voice-currents. 1 r

The object of my invention is,"in general,

- to provide a system which will be marked by greater simplicity inv the arrangement and- 7 central office.

character of the switchingapparatus at the More particularly, object is to provide a system of circuits for use in multiple switchboards wherein, although two conductors may be used for each telephone-line between the substation and the central oflice, automatic operation of the supervisory signals, together (with efficient transmission of;telephonicland "ringing current, may be secured by the extension through the multiple switchboard ofbut or more conductors usually employed.

To this end an important feature of my invention consists in conductively dividing a to the substation a source of current anda .magnetic switch'controlled by the switchhook atthe; substation andincluding directly in the connecting cord-circuit by means of trolled by the magnetic switch when connection is made with the line.

ciating it with the circuit that it operates to display the line-signal when the circuit of the line is closed at the substation and to efface it when connection is made with the line.

Other features of hereinafter. v Y Iwill'describe my invention more particularly with reference: to the accompanying drawing, which illustrates by means of contending from their respective substations'to a central ofiice and thereprovided with a connecting cord -circuit for uniting them, the

, ance with my invention. v

tors 1 2, which extend from theusual telephonic apparatus at the substations A B to the central oflice O. In the circuit of the line the winding of-a line-relay a, shunted ,bya non-inductive'resistance a; a central battery Z ,*one pole of which may be grounded; a resistance 0, and one winding, d, of a repeatingprovided with an armature and acts both as a repeating-coil anda relay, I will refer to it hereinafter asa repeating-coil relay. The

repeating-coil relayd contains two other windtelephone-line by means of an induction device including in that portion which extendsi i Another feature of my invention consists in so'constructmgthe'lnduction devlce and asso-" Ti whole being equipped and arranged in accordings,d and .12 which are included serially ink;

one conductorfor each line instead of the two 7 my invention will appear ventional "symbols two telephone lines ex- Each telephone-line comprises two conducl conductors at the central ofiice are included coil 03. Inasmuch as this repeating-coil is 60 which one telephone-line is unitedto another-" a signal, with means for operating it cona conductor 3, which extends from the contacts of jacks e e to earth or a return-conductor. One of these windings d is short-circuited in normally closed contacts of relay a. The repeating-coil relay d is so arranged that a certain magnetizing force will cause the armature to be attracted to close a contact, while any magnetizing force in excess of this predetermined amount will cause the armature to be attracted further to break one contact and close another. Relays adapted to act in this manner are old in the art and of widelyvarying structure. In the form which I have illustrated a lever F normally rests against the contact-point d The armature d when attracted is adapted to make contact with lever cZ* and move it away from contact-point d and against contact-point d. The normal pressure of lever d against contact-point 0? may be so regulated by means of a light helical spring d that any attractive force less than a predetermined amount will merely v serve to move armature d into contact with lever d without breaking the contact between the lever d and contact-point d while if the attractive force is in excess of this predetermined amount the retractile force of spring cl will be overbalanced and contact will be made through the medium of lever d between armature OZ and contact-point 6Z7. A signal-lamp j" is associated with the answering-jack e of the line and is included in the circuit 4, which extends from the free pole of the central battery 6 to contact d of the contact with lever 03* without causing said lever to move away from contact-point d the circuit 4 is completed and the signal-lamp f is illuminated. When the attractive force is such that the armature is drawn up to its full extent, the connection between armature d and contact-point 0Z through the medium of lever d is broken, while the connection between armature (Z and contact d through the medium of the lever is completed. This action opens circuit 4:, thereby causing the lamp f to be extinguished, and completes a short circuit of resistance 0. The resistance cis includedin the circuit of the line in order to prevent the current-flow through the line-circuit, should the resistance of the line happen to be low, from rising when the telephone is taken off the hook to that value where the magnetizing force generated in repeating-coil relay d would be suflicient to move its armature (i to interrupt the circuit of line-signal f instead of closing it. When connection is 1 completed with the line, the resistance is no longer required and is therefore short-circuited in order that it may not impede the flow of transmission-current.

The connecting cord-circuit comprises plugs g g, united by a conductor 5, which includes serially the two supervisory signal-lamps it h and the two windings of a repeating-coil The battery 6 is connected in a bridge to ground from a point in the cord-circuit intermediate of the two windings of the repeatingcoil c'. The operators telephone apparatus and a source of ringing-current Z are associated with the connecting cord-circuit and controlled by keys in the usual manner. The calling-plug g of the pair is furnished with an auxiliary contact-piece or test-tip 7, which may be permanently connected, through a third winding of the operators ind notion-coil, to ground. This test-tip is adapted to project beyond and be insulated from the linespring of the jack into which it may be inserted, its only function being to indicate the presence of a test potential on the jack of a busy line into which it may be inserted. The windings of the repeating-coil z' and the supervisory signal-lamps h it are preferably of low resistance, each winding having a resistance of, say, forty ohms and each lamp a resistance of, say, twenty ohms and requiring a current of approximately two-tenths ampere for its illumination. The resistance of winding 0? of the repeating-coil relay (Z may be two hundred and fifty ohms. The resistance of winding 0Z may be one hundred and seventy ohms, and the resistance of winding 03'' may be eighty ohms. The resistance of resistance-coil cmay be five hundred ohms and the electromotive force of the central battery 5 twenty-four volts.

Although three batteries have been shown for the sake of clearness in the drawing, it will be understood that in accordance with the usual practice these may be one and the same battery.

The operation of the system is as follows: The subscriber at substation A desiring connection with another subscriber-say the su bscriber at substation Btakes his telephone from the hook and in so doing allows the telephone-switch to close its contacts and complete the circuit of the telephone-line. The current flowing from battery 6 in the circuit thus completed energizes the magnets of relay a and repeating-coil relay d and causes them to attract their armatures. The armature of relay a in drawing up breaks the normal short circuit of winding (Z of repeatingcoil relay d. The magnetizing force generated under these conditions in the repeating-coil relay d is only suflicient to cause armature 03 to be attracted into contact with lever 03 without forcing lever al away from the contactpoint CF. The circuit of conductor 4 is thus completed and line signal-lamp f is illuminated. The operator upon seeing the illumination of lamp f inserts the answering-plug IIO :g of a pair of connecting cords' into the answering-jack 0', associated with the lighted lamp. Current then flows from battery I) through circuit '3,completed in register- 5 ing-contacts of the'answering plug and-jack, this circuit including one winding of repeating-coil t, supervisory lamp h, and windings (Z andol. of the repeating-coil relay. The short circuit of'winding d of the repeating- IO coil relay beingbroken in contacts of relay a, current flows through windings d and (Z and the attractive force generated thereby in addition to that generated in winding dis suflicient-to' cause armature d -to sever con-' force upon the armature. The current which" flows through the circuit-composed of con.- ducto'rs 5 3.and the included apparatus isinsuflicient toilluminate supervisory lamp/1,,

which consequently remains dark. As the windings d of the repeating-coil relayare in inductive relation with thewindin-g d,

which is included in the circuit of the tele- 3o phone-line l 2, extending to the calling-substation, the operatorby operating the key which'connects her telephone circuit'with the line may place herself in communicationwith the calling-subscriber'and. inquire the num- 3 5 ber of the line with which he desires'connee tion. Upon learning this she-Itests by touching the test-ting of the calling-plug of the *pair of cordsto the multiple jackeof the linev called for and finding that the line is notiin,

use inserts the plug and'by depressing-key 70 causes.ringing-current fromthe' grounded source Z to How through winding d ofre; This induces a current i 'peating-coil relay d. in winding d, which being included in the linecircuit effects the operation. of the bell at station B. When the calling-plug is first inserted.

, in the jack of the calledliriB, current flows-to earth from battery I through supervisory lamp Ii, by way of conductors 5, 3' and wind- 5 ing di'of -the repeating-coil relay associated.

with; the called line. Until the called subscriber respondsto the call windingul' of the repeating-coil relayof hi's'line is short-circuited in the normally closed contacts of the relay 0 of'the called line. The resistanceof winding diis' made low, as 'hereinbe'fore dea s'cribed, so that under these conditions the flowofcurrent through thecircuit 5: 3 is sufficient to cause the illumin ationof supervisory lamp [2,. 1 The "comparatively heavy current which flows in the circuit of conductors 5 3,

owing to'windirngd of .the repeating-cpilrelay associated'ywith thecalled line being shortcircuited, is suflicient to generate anattractive 5 'force in the repeating-coil"relaywhich draws .and a winding of a repeating-c oil included in I extending from a substation to a centrallofiice,

the armature up as far as it will go, thus breaking the-circuit of the line signal-lampfof the calledline and completing the short-circuit of resistance 0 as soon as the calling-plug is iri serted. When the subscriber, responding to the ringing'of his bell, removes histelephone from the-hook,circuitis immediately com- (pleted for current to flow from battery I) over the line conductors l 2 through the included apparatus at the substation in the central office. This current flowing through relay d causes it to operate to break the short circuit of winding d of the repeating-coil relay. The additional resistance which is thus thrown into the circuit of conductors 5 3 is suflicient toso .80 reduce the current flowing therein that the supervisory lamph is extinguished. The current-which, as soon as the called subscriber removes his telephone from the hook, circulates in windingpl" of the repeatingcoil relay is such as to augment the efiectof that which: has, been circulating in winding d and which uponthe actuation of relay a flows serially through windings 0Z and d so that the armature 0Z is held in the same position to which '90 it was moved by the current primarily flow:

ing in winding (2 -When the subscribers have finishedjtheir conversation, the replacing of their telephones upon the ,hooksbreaks, the circuitiof the lines and causes the deener gization of line-relays a a. The armatures of these relays falling back reestablish the normalshort circuitsof windings d d of the repeating-coil relays associated withtheir linepeating-coil relays d d is caused-to flow. The t illuminationof both supervisory signal-lamps istaken by the operator as a signal forv dis- 7 connection. I V 'Having'thus described my invention, Iclaim as new, and desire to secure by Letters Patent, thefollowingf V 1 1. The combination with a telephone-line extending from a substation to a central ofiice, of a switch at the substation controlling the circuit of. the line, a sourceof current, a relay,

I I 5 the circuit, of the line at the central ofiice, a local telephone-circuit,a second winding of the repeating-coil, a source of current,:and a signal device included therein, and means controlled by the aforesaid relay adapted to vary the resistance of the local circuit to efiectthe actuation of the'signal device, substantially as. described.

'2. The combination with a telephone-line I 2 5 of fa line-relay, one winding of a'repeatingcoil, and a source of current included in the circuit of the line at the central office, a switch for controlling the circ'uitof the line a t-the substation, a connection-terminal for the line, 3

and means for making connection with the line at said connection-terminaLa second winding for said repeatlngrcoil, and a local circu t therefor completed at said connection-terminal .in making connection with the line, a sig- I of a switch at the substation for. controlling the flow of currentin the line, a-sourceiof current, and a relay in the circuit of the line at the central oflice, said relay being also adapted to act .as a repeating-coil, a line-signal displayed through the agency of said relay, a spring-jack for the line, a plug and plug-circuit for making connectiontherewith, a second winding of the aforesaid relay in induct- 1 ive relation with the first-mentioned winding, and a local circuit therefor completed in .making connection with the line, a signal device and a source of currentin said localcircuit, the flow of current in said local circuit operating to actuate the signal device and to operate the aforesaid relay to efface the linesignal, and a second relay in the circuit of the line controlled by the telephone-switch at the substation operating to alter the resistance of the local circuit to effect the deenergization of the aforesaid signal device, substantially as described.

4. The combination with two telephonelines, each extending from a substation to a central office, of a source of current, a line-relay, and one winding of a repeating-coil in the circuit of each line atthecentral office, a switch at each substation for controlling the flow of current in the line, a second winding for each repeating-coil, a springjack for each line connected with one terminal of said second winding, the other terminal being connected to earth, a pair of plugs and a single conductor plug-circuit for uniting the lines at .the spring-jacks thereof, an inductive device 'conductively dividing the plug-circuit, a

grounded source of current connected with the plug-c1rcu1t through the induction device,

supervisory signals included in the plug-cira switch at the substation of each line for determining the flow of current therein, a springjack for each line and a pair of plugs and their plug-circuit for uniting the lines at the spring-jacks thereof, a second winding for each repeating-coil, one terminal of said winding being connected to earth and the other terminalto the spring-jack of the line, two signals included in the plug-circuit, a grounded source of current connected with the plugcircuit at a point between the two signals, and a relay in the circuit of each line adapted to vary the resistance of the circuit including the secondwinding of the repeating-coil, whereby the signals in the plug-circuit are controlled.

6. The combination with two telephonelines extending from substations to a central office, and a link conductor temporarily uniteoil interposed in the circuit of one of the lines, said repeating-coil having three windings, one of, said windings being included with a source of current in the circuit of that portion of the line extending to the substastation, the other two windings being included serially in the circuit of that portion of the line united to the other telephone-line through the link conductor, a signal and a source of current also included in the circuit with the two last-mentioned windings of the repeating-coil, said signal being adapted to operate upon an increase of current, a short circuit of one of the two last-mentioned windings of the repeating-coil, an electromagnetic switch for controlling the same included in -.the portion of the line extending to the substation, and a switch at the substation controlling the circuit oftthe line, whereby the signal is actuated.

7 The combination with two telephone-lines extending from substations to a central ofli e, and a link conductor temporarily uniting; the same for conversation, of a repeating-coil iiiterposed in the circuit of one of the lincs,said repeating-coil having three windings, one of said windings being included with a source of currentin the circuit of that portion of the line extending to the substation,the other two windings being included serially in the circuit of thatportion of the line united to the other telephone-line through the link conductor, a

signal and a source of current also included in the circuit with the two last-mentioned windings of the repeating-coil, said signal being adapted to operate upon an increase of current, a short circuit of one of the two lastmentioned windings of the repeating-coil, an

electromagnetic switch for controlling the same included in the portion of the line extending to the substation, a switch at the substation controlling the circuit of the line, an armature for the repeating-coil, and a linesignal controlled thereby, substantially as described.

8. The combination with a telephone-line ITO extending from a substation to a central oflice, and a switch for controlling the circuit of the same, of a source of current and a winding of a repeating-coil included in the circuit of the line at the central oflice, alocal telephone-circuit including anotherrwindingof the repeat-1 ing-coil and a source of current, a switch for completlng said local clrcuit 1n making connection with the line, an armature forthe recuits, of a repeating-coil having a windingin each clrcult, a source of current anda swltch v in each circuit for controlling the flowof cur rent therein, an armature for the repeating- -coil and contactscontrolled thereby, and a signal having a circuit controlled'in said contacts,the windings of the repeating-coil being so proportioned that the attractive force produced by current flowing in one of the windings alone moves the armature part Way to close said signal-circuit,' while current flowing in the other winding or in both windings at once attracts the armature further to open the signal-circuit.

In witness whereof I hereunto subscribe my name this 23d day of J uly, A. D. 1902.

. CHARLES E. SCRIBNER. Witnesses: EDWIN H. SMYTHE, 'FREDERICK A. WATKINS. 

